Description

Glucose transporters are integral membrane glycoproteins involved in transporting glucose into most cells. Seven types of glucose transport carrier proteins, designated as Glut 1 to 7, facilitate glucose transport across the cell membrane. Molecular cloning of glucose transporters have identified a family of closely related genes that encode at least 7 proteins exhibiting high degree of amino acid homology (45% to 65%), all in the molecular weight range of 40 to 60 kDa. Individual members of the Glut family have predicted secondary structure characteristic of 12 membrane spanning domains of other transport carriers. The majority of differences in sequence homology in Glut proteins occur at 4 hydrophilic domains that may play a role in distinct tissue specific pattern of expression and targeting. All Glut proteins are glycosylated at or near the C terminus and are present on either cell surface or in intracellular sites. Some transporters exhibit dynamic trafficking between intracellular storage sites and plasma membranes in response to various stimuli. In some tissues Glut proteins are asymmetrically distributed between apical and basolateral membranes as in blood brain barrier and blood testis barriers.